The flip mentality is people who can use the iPad as their only, or primary device do simple work that can be done on ancient computers.
So I don't like those broad statements, because while you are correct, it paints a broad brush and assumes the inability to those things are important to all people.
Can I do everything I can on my Mac on my iPad? No. That doesn't negate the iPad since the primary, non-day job work I do is drawing and writing. I find the iPad more conducive to those tasks. Procreate is an amazing app, as is Affinity Photo. While Ulysses is close to feature complete between the two OSs, at this point my muscle memory is better on iOS for a lot of tasks.
I can even do a lot of my day job on the iPad. Even those of us who create output as part of our jobs don't usually spend 8 hours a day creating that output. I've got two documents I need to do this week, and I've probably spent about 2 hours working on them. Why? Meetings after meetings after meetings. The iPad is great for taking notes on, or dealing with emails, and the general day to day minutia that wears down life in corporations. Even with how half-featured Word is on the iPad I could still get a lot of my documents done on the iPad.
I don't often find myself needing to get into the Terminal, or attach a USB storage device, or rip a CD into iTunes. I don't like printing out paper that is just going to get tossed into a recycle bin after the meeting. I don't want to get too far down that rabbit hole since it is easy to move the goalposts on both sides.
If those types of things, and other things you need a Mac for are tasks people do every day, well, Apple still makes the Mac and will for a while.